Railway signaling apparatus



Aug. 13, 1940. H. G WITMER 2,211,190

RAILWAY SIGNALING APPARATUS Filed May 27. 1939 f 10) l 6,:- 2- Code ansmz'zlel? C uw T5 54 Fly. I.

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HS ATTORNEY Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE appagante May er, 1939, serial No. .276,201

8 Claims.

My invention relates to railway signaling apparatus, and more particularly to railway signaling apparatus used in connection with coded track circuits.

In railway signaling apparatus heretofore used with coded track circuits an undesirable clear signal condition may be intermittently created while a train occupies a track circuit because with a poor train shunt occasional current impulsesv may reach the track relay of sufcient magnitude to operate the track relay. Especially is this true on railways having light weight high speed trains. I propose according to my present invention to avoid such undesirable signal conditions by requiring operation of the code following track relay at the respective cod-e rate for a predetermined period before a clear signal condition is made effective and by checking that the track relay is operated in response to each individual current impulse of the track circuit.

Accordingly an object of my invention is the provision of novel and improved means for use with a railway track circuit supplied with coded current wherewith the signal control condition corresponding to occupancy of the track circuit is uninterruptedly enforced if the train passing over the track circuit is effective to shunt even one current impulse of the coded track circuit current out of several successive impulses. That is, the control condition corresponding to occupancy of a track circuit is maintained in response to a train shunt that is effective only intermittently and a false clear signal condition due to a loss of train shunt is avoided unless such loss of train shunt persists for an interval greater than an interval predetermined for the track circuit. Other objects and advantages of my invention will appear as the specication progresses.

I shall describe two forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Figs. l and 2 are diagrammatic views of two different forms of apparatus, each of which embodies my invention. In each of the two views like reference characters designate similar parts.

Referring to Fig. 1, the track rails la and lb of a, stretch of railway over which traiic normally moves in the direction indicated by an arrow are formed by the usual insulated rail joints with a track section W-X, and which section may be one section of a series of consecutive sections of a signal system. The track section W-X is provided with a track circuit having a source of coded current connected with the rails at the exit end of the section and a code following track relay connected with the rails at the entrance end of the section. The source of coded current may take different forms and in the present case it supplies coded direct current of the impulse type, the source consisting of a track battery TB, a code transmitter CT and a track transformer TF.

'I'he construction of the code transmitter CT is immaterial and may be any one of several well-known types and in Fig. 1 is of the relay type whose operating winding 2 is permanently connected with a current source so that its contact member 3 is operated to periodically engage a stationary contact l at a predetermined rate' such as, for example, 75 times per minute. When contact 3--t of the code transmitter CT is closed, a simple circuit is completed by which current flows from the track battery TB to the primary winding 5 of the track transformer TF. The secondary winding 6 of track transformer TF is connected across the rails la and Ib over wires 1 and 8, and a condenser 9 is connected across the primary winding 5. Hence, when contact 3-4 of the code transmitter is closed, primary winding 5 of the track transformer is energized and energy is stored in the magnetic circuit of transformer TF and condenser S is charged. The parts are so proportioned as to time constant for the circuit that the magnetic energy builds up relatively slow and no energy is inductively transferred through transformer TF to the track rails, or at least the magnitude of the energy transferred at this time is so small it can be neglected.

Each time the contact member 3 of code transmitter CT breaks engagement with contact 4, the magnetic energy stored in transformer TF causes a high voltage to appear across the terminals of condenser 9 and by transformer action a proporticnately high electromotive force is induced in secondary winding 6 and, in turn, is impressed on the track rails of section W-X. This electromotive force causes a current impulse having a damped wave form to flow in the track circuit. The amplitude of the first half cycle of the wave form of such current impulse has a relatively high peak voltage and is materially larger in amplitude than any of the following half cycles of the current impulse. Such high peak voltage of the current impulse is desired as an aid to the shunting sensitivity of the track circuit by breaking down the rail lm resistance of the wheelrail contacts when the track circuit is occupied. Hence, the rst half cycle of each current impulse is the dominating half cycle and the current impulse in effect can be considered as consisting of a single half cycle of unidirectional current having a relatively high peak voltage.

The parts are further so proportioned that such half cycle of unidirectional current supplied to the track circuit is preferably of short duration and only a low energy output of the track 'oattery TB is required. Furthermore, the duration of such current impulse is preferably only a small portion of the operating cycle interval of the code transmitter so that the duration of each current impulse is short as compared with the duration between successive current impulses. It follows that as long as the winding 2 of code transmitter CT is energized and the code transmitter is active, the track circuit of section W-X is supplied with coded or time spaced impulses of unidirectional current of a given polarity and which impulses are preferably of high peak voltage and have a duration which is relatively short as compared with the duration between successive impulses.

It will be understood, of course, that I do not wish to limit my invention to coded current having 75 impulses per minute or having impulses of current of high peak voltage and short duration as described above, but that. such code rate and characteristics have been found satisfactory for coded railway track circuit current.

A code following track relay CF has a rst or operating winding Ill connected across the rails at the entrance end of section W--X over wires II and I2, a resistor I3 being preferably interposed in wire II. The relay CF is provided also with a second or holding winding I l which will be referred to hereinafter.

The code following relay CF may be either of the direct current neutral or polar type and, in this instance, it is a quick acting polar relay having polar Contact members I5, I6 and il which are biased to seek the normal or left-hand position as viewed in Fig. 1 when the relay is deenergized as well as being held in the normal position when the relay is energized at normal polarity. When relay CF is energized at reverse polarity, the contact members I5, I6 and II are operated to the reverse or right-hand position as viewed in Fig. 1. The connection of operating winding I with the track rails is such that the coded unidirectional current impulses supplied to the rails through transformer TF and its associated apparatus cause relay CF to be energized at reverse polarity so that its contact members I5, IE and I'I are operated to the reverse position where they engage reverse contacts I 8, I!) and 2B, respectively. During each interval between successive impulses of the track circuit current and relay CF is deenergized, the contact members I5, I6 and I 'I are operated b-y the biasing element of the relay to the normal position where they engage normal contacts 2l, 22 and 23, respectively. Consequently, the track relay CF is operated at a rate corresponding to the code rate of the track circuit current impulses. However, as far as the energization of the operating winding lil of relay CF by the track circuit current impulses is concerned, the contact members I5, I6 and I'I are made to engage the respective reverse contacts for only a brief period for each current impulse due to the short duration of the current impulse, whereas the period the Contact members I5, I6 and I'I engage their respective normal contacts is relatively long due to the relatively long duration between successive current impulses of the track circuit current. In other words, the coded track circuit current impulses of section W--X alone would operate the code following relay CF at unequal on and off periods.

With track relay CF operated and contact member E made to alternately engage reverse contact I3 and normal contact ZI, direct current is alternately supplied to two portions of the primary winding 24 of a decoding transformer TD. To be explicit, when reverse contact I5-I8 is closed. direct current from a source, whose terminals are indicated at B and C, ows through the lower portion of primary winding 24, and when normal contact I52I is closed, current from the same source iiows through the top portion of primary winding 24. With direct current thus alternately supplied to the two portions of primary Winding 24, an alternating electromotive force is induced in secondary winding 25 of transformer TD.

To equalize the on and off operating periods of track relay CF, the holding winding I4 of relay CF is connected with the secondary winding 25 of transformer TD over reverse contact ITL-2U of relay CF; and the connection of the holding winding I4 is made such that the polarity of the electromotive force induced in secondary winding 25 when current builds up in primary winding' 24 due to the closing of reverse contact I5-I8 of relay CF, causes relay CF'to be energized at reverse polarity. The energization thus effected through holding winding I4 aids the energization elfected by the track circuit current impulse iiowing in the operating winding Ill. After a brief period, the electromotive force induced in secondary winding 25 falls to zero and the current flowing in holding winding I4 of relay CF falls to zero so that relay CF is deenergized and'its contact members are operated by the biasing element of the relay back to the normal position.

The parts are so adjusted that the energization of relay CF as effected through the holding winding lli persists for an interval after the track circuit current impulse ceases to flow in operating winding Ill and relay CF is operated at substantially equal on and off periods. This manner of equalizing the on and olf periods of the code following relay CF forms no part of my present invention and is disclosed and claimed in a copending application for United States Letters Patent, Serial No. 274,414, filed May .1.8, 1939, by E. J. Agnew for Signaling apparatus. It is to be noted that with apparatus embodying my invention such means for equalizing the on.and off periods of the code following relay CF while helpful may not be needed.

According to my invention, the electromotive force induced in secondary winding 25 of decoding transformer TD in response to operation of the code following track relay CF is used to control a signal control circuit through the means of a time element relay DT and another relay RI.

The time element relay DT may take diierent forms and preferably is of the construction covered by the United States Letters Patent No. 1,966,965, granted July 1'?, 1934, to Branko Lazich and Harrey E. Ashworth, for Electrical relays, and to which patent reference is made for a full understanding of such time element relay. It is suiiicient for the present application to describe relay DT but briey by pointing out that relay DT is provided with an initial position and an operated position. When relay DT is deenergized, it at once moves by gravity to its initial position where its contact members 26, 2'I and 28 enga-ge respective back contacts and a check contact 23--39 is closed. When relay DT is energized, it moves in a step by step manner from its initial position to its operated position, check contact 29-38 being opened shortly after the relay leaves its initial position and the contact members 26, 2l and 23 remaining in engagement with their respective back contacts until the full `operated position is reached where they are moved to engage respective front contacts. Further energization of relay DT after it has been operated to its operated position retains the relay at its operated position with the check conw tact 29-30 open and the contact members 25, 21 and 28 in engagement with their respective front contacts. The time required by relay DT to move from its initial position to its operated position can be adjusted for any predetermined period over a relatively wide range, for example, any predetermined period between l seconds and minutes. In Fig. l, when relay DT occupies its initial position, the contact member 21 engages a back contact 3! and the check contact 12S- 39 is closed. At the operated position, conv tact members 26 and 28 engage front contacts 3,2 and 33, respectively, and check contact 29-39 is open.

The relay RI is a .standard direct current neutral relay which is preferably made slightly slow releasing in character.

Normally, that is, when section W--X is unoccupied and code following relay CF is operating in response to the coded current supplied to the track circuit of section WiL-X, the time ele- .ment relay DT is held energized at its operated position and relay Rl is deenergized and released, relay DT being held energized over a stick' circuit supplied with current by virtue of the electromotive force induced in the secondary Winding 25 of decoding transformer TD in the manner described hereinbefore. The contact member i6 of relay CF alternately connects two portions of secondary winding 25 to the stick cirvcuit for relay DT so that the alternating electromotive force induced in secondary winding 25 is rectied and current flows in the winding of relay DT always in the same direction. This stick circuit 'for relay DT can be traced from the mid terminal of secondary winding Z5 over wire 34, winding of relay DT, front contact 32 and contact member ZS Aof relay DT, wire 35, and either normal contact Iii-22 of relay CF to the top terminal of secondary winding 25, or reverse contact l-l of relay CF to the bottom terminal of secondary winding 25. Since contact member H5 of relay CF is operated in step with contact member I5, the alternating electromotive force induced in secondary winding Z5 is rectied and unidirectional current ilows in relay DT always in the same direction and that relay is eiectively energized thereby. It is to be noted that when code following relay CF is operated at a code rate ofthe order of 75 cycles per minute as here selected for illustration or some higher rate, the energization of time element relay DT does not ordinarily at least fall below the value at wl'nch relay DT releases during the interval between successive impulses of the unidirectional current impulses but is released if one track circuit current impulse is missing so that there is a correspondingly extended interval during which relay D'I is not energized. If a low code rate is used relay DT may be made slightly slow to release.

Relay DT controls a signal control circuit, the

signal control ycircuit kin Fig. 1 .including front contact 33 and contact member 28 of relay DT.

When a train enters section W-X and shunts the track circuit so that the code following relay CF is made inactive and remains at its no-rmal position, no energy is supplied through the decoding transformer TD to time element relay DT with the result relay DT is deenergized and immediately restored to its initial position by gravity, the signal control circuit being opened at front contact 33 of relay DT to establish a signal control condition coresponding to occupancy of the track section.

When time element relay DT is restored to its initial position and check contact 29-38 is closed, a simple pick-up circuit, easily traced, is completed for relay RI and that relay is energized and picked up closing its front contacts 36 and 3l. Assuming the train shunt remains constantly in effect as the trainA passes through section W-X, code following relay CF remains inactive, time element relay DT remains at its initial position `with the signal control circuit set to correspond to occupancy of the track circuit, and relay RI is picked up.

When the train vacates section W-X and relay CF is again operated by the coded track circuit current so that an eiectromotive force is again induced in secondary winding 25 o-f transformer TD, rectiiied current is supplied to the time element Vrelay DT over a pick-up circuit, which pick-up circuit can be traced from the mid terminal of secondary winding 25 over wire 3s, winding of relay DT, front contact 3l of relay Rl, wire 35, and either normal contact |22 of relay CE' to the top terminal of secondary winding 25, or reverse contact IE-IQ of relay CF to the bottom terminal of secondary winding 25. Time element relay DT is now moved from its initial position to its operated position in the period predetermined by the adjustment of the relay. When check contact 29--39 is opened as relay DT moves away from its initial position, the relay RI is retained energized over a stick circuit `which includes terminal B of the current source, contact member 2l and back contact 3l of relay DT, front contact 35 and 'winding of `relay Rl and terminal C of the current source.

At the end ci the predetermined operating period of relay DT, its contact members 26, 21 and 28 are picked up, closing the stick circuit for relay DT at front contact 33 sc that the time element relay is then retained energized by current supplied to its stick circuit due to the electromotive force induced in secondary winding 25. 'The signal control circuit is now closed at front contact 33 of relay DT to effect a signal control condition corresponding to section W-X being unoccupied. With relay DT picked up opening back contact 3l, the relay Rl is deenergized and released at the end of its slow release period, the apparatus being now fully restored to its normal position.

In the event the train shunt is not constantly effective while the train occupies section W-X 'and at times current impulses reach relay CF of surlcient magnitude to operate relay CF, the signal control circuit is not affected unless relay CF is operated at its usual rate for a period sufficient to cause relay DT to move from its initial position to its operated position. If the train shunt is effective to shunt even a single current impulse away from relay CF during the period required to move relay DT, the relay DT is immediately restored to its initial position.

I have found that when time element relay DT is adjusted at a predetermined operating period satisfactory for railway signal systems a train shunt effective to shunt one current impulse out of every ten consecutive impulses of the track circuit causes the condition of the signal control circuit corresponding to occupancy of the track section to be steadily established.

It is clear, therefore, that apparatus embodying my invention when used with coded track circuits assures reliable control of the signal circuit by present day high speed lightweight trains which may effectively shunt the track circuit only intermittently.

In Fig. 2, the apparatus is the same as in Fig. 1 except for the manner of controlling the time element relay DT and relay Rl. In Fig. 2, the relay RI is preferably of the usual acting type and is normally energized and picked up in response to rectified current supplied by virtue of the electromotive force induced in decoding transformer TD, and the time element relay DT is energized from a local current source over a front contact of relay RI. Relay Rl may be of a construction that requires a relatively low energy level for proper energization thereof as compared with the energy lever required for proper energization of the time element relay DT. Hence operation of relay Rl by the energy supplied through the decoding transformer and operation of the time element relay from a local current source may be more satisfactory.

It is thought that the apparatus of Fig. 2 can best be understood by a description of its operation. W'hen section W-X of Fig. 2 is unoccupied, the coded or time spaced impulses of current supplied to the rails at the exit end of the section cause track relay CF to be operated at a corresponding code rate and. direct current is alternately supplied over normal contact i5--2l and reverse contact l5-l8 of relay CF to the two portions of primary winding 2A', of decoding transformer TD so that an alternating electromotive force is induced in the secondary winding 25 of transformer TD in the same manner as described in connection with the apparatus of Fig. 1. Rectied current is supplied to relay Rl over a stick circuit which includes mid terminal of secondary winding 25, wire 38, front contact 39 and winding of relay Rl, and either normal contact l622 of relay CF to the top terminal of secondary winding 25 or reversev contact IG-l 9 of relay CF to the bottom terminal of secondary winding 25. It is to be pointed out that with a code rate of the order of 75 impulses per minute for the track circuit current the relay Rl is not ordinarily at least released during the interval between successive impulses of the rectified current but is released if one track circuit current impulse is missing. As stated hereinbefore relay RI may be slightly slow releasing in character. With relay RI picked up closing front contact 4U. a simple circuit is completed for energizing the time ele ment relay DT from a local current source whose terminals are indicated at B and C. Time element relay DT, when moved to its operated position, completes a signal circuit at its front contact 33 the same as in Fig. l.

When a train enters section W-X of Fig. 2 and shunts the track circuit so'that code following relay CF is inactive and no current is supplied to relay R! through the decoding transformer, relay Rl is at once released, opening front contact 4D interposed in the circuit of the time element relair DT. Time element relay DT is, in turn, deenergized and at once restored to its initial position, opening the signal control circuit at front contact 33 to establish a restrictive signal condition, and closing check contact 29-30 to check the initial position of relay DT.

When the train vacates section W-X and relay CF is again operated by the coded track circuit current, relay Rl is first energized over a pick-up circuit, which pick-up circuit is the same as the stick circuit traced for that relay except to include the check contact 29-30 instead of front contact 39 of relay Rl, check contact 29-30 forming a shunt path around front contact 39. With relay RI picked up closing front contact 40, the time element relay DT is energized and slowly moves from its initial position to its Aoperated position in the predetermined time interval at which that relay is adjusted, the signal control circuit being closed at front contact 33 when the full operated position of relay DT is reached. The check contact 29-30 is opened shortly after relay DT moves away from its initial position, but relay RI once picked up is retained energized over its stick circuit' supplied by energy through the decoding transformer as described hereinbefore.

It is clear that in the event of a loss of train shunt when a train is passing through section W-X of Fig. 2, code following relay CF may be operated and relay RI may be picked up, but the signal control circuit remains open until the time element relay DT has had time to move from its initial position to its operated position. Also, if the train shunt is effective during a part of the time that the time element relay DT is being moved from its initial position to its operated position, the time element relay DT is at once deenergized and restored back to its initial position so that a train shunt intermittently effective causes the signal control circuit to be steadily retained at the condition corresponding to occupancy of the track section.

Although I have herein shown and described only two forms of apparatus embodying my invention, it is understood that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In combination with a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section, a time element relay having an initial position and an operated position and characterized by a slow movement from its initial position to its operated position when energized and a relatively quick movement back to its initial position when deenergized whereby said time element relay is moved to its operated position only when effectively energized for a predetermined period and is reset to its initial position when such energization is momentarily interrupted, a signal circuit including a contact of said time element relay closed only at said operated position, and decoding circuit means controlled by said code following relay effective to cause such effective energization of said time element relay only when said code following relay is operated by each successive track circuit current impulse occurring within said predetermined period.

2. In combination with a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section, a time element relay having an initial position and an operated position and characterized by a slow movement from. its initial position to its operated position when energized and a relatively quick movement back to its initial position when deenergized whereby said time element relay is moved to its operated position only when effectively energized for a predetermined interval and is reset to its initial position when such energization is momentarily interrupted, a check contact for said time element relay closed only at said initial position, another contact for said time element relay closed only at said oper ated position, a signal circuit including said other contact, a first circuit means controlled by said track relay and including said check contact to initially energize said time element relay when the track relay is operated, and a second circuit means controlled by said track relay when oper ated to energize said time element relay and effective only when such energization has been initiated by said first circuit means.

3. In combination with a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code iollowing track relay responsive to such current impulses connected across the rails at the other end of the section, a time element relay provided with a contact which is closed only when that relay is effectively energized for a predetermined period, decoding circuit means controlled by said track relay to energize said time element relay and operative to eectively energize said time element only when said track relay is operated by each successive track circuit current impulse occurring within said predetermined period, and a signal circuit including said contact of the time element relay.

4. In combination with a track circuit for an insulated railway tra-ck section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section, a time element relay having lan initial position and an operated position and characterized by a slow movement from its initial position to its operated position when energized a predetermined period and a quick movement back to its initial position when deenergized, a check contact and another contact for said time element relay, said check contact closed only at said initial position and said other contact opened only at said operated position, another relay, a pick-up circuit for said other relay including said check contact, a Stick circuit for said other relay including said other contact, pick-up circuit means for said time element relay controlled by said track relay and including a iront contact oi' said other relay and effective to energize said time element relay only when said track relay is operated by said track circuit current impulses, stick circuit means for energizing said time element relay controlled by said track relay when operated by said track circuit current impulses, and a signal circuit controlled by said time element relay when moved to its operated position.

5. In combination with a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section, a time element relay having an initial position and an operated position and characterized by a slow movement from its initial position to its operated position when effectively energized a predetermined period and a quick movement back to its initial position when deenergiaed, a check contact and another contact ior said time element relay, said check contact closed only at said initial position and said other contact opened only at said operated position, another relay, a pick-up circuit for said other relay including said check contact, a stick circuit for said other relay including said other contact, a pick-up circuit for said time element relay including a front contact of said other relay, a stick circuit for said time element relay, current source means controlled by said track relay to supply current to said pick-up circuit and said stick circuit of said time element relay and effective to supply such current for errectively energizing the time element relay only ywhen said track relay is operated by each successive current impulse of said track circuit, and a signal circuit including a contact of said time element relay closed only at said operated position.

c. In combination with a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section, a time element relay having an initial position and an operated position and characterized by a slow movement from its initial position to its operated position when energized a predetermined period and a quick movement back to its initial position when deenergized, a check contact and another contact for said time element relay, said check contact closed only at said initial position and said other contact closed only at said operated position, another relay, a circuit including a front contact or said other relay to energize said time element relay, a pickup circuit including said check contact for said other relay, a stick circuit for said other relay, current source means controlled by said track relay to supply current to said pick-up circuit and said stick circuit of said other relay and eective to supply such current for effectively energizing said other relay only when said track relay is operated by each successive current impulse of the track circuit, and a signal circuit including said other Contact of the time element relay.

7. In combination with a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section; a time element relay having' an initial position and an operated position and characterized by movement from its initial position to its operated position when energized uninterruptedly for a predetermined period, held in said operated position when subsequently energized uninterruptedly and reset immediately to its initial position when deenergized; another relay, means including a front Contact of said other relay and a current source to energize said time element relay, decoding circuit means connected with a winding of said other relay and controlled by said track relay to supply current effective to energize said other relay in response to operation of said track relay, and a signal circuit including a contact of said time element relay closed only at said operated position.

8. In combination With a track circuit for an insulated railway track section including means to supply time spaced impulses of current to the rails at one end of the section and a code following track relay responsive to such current impulses connected across the rails at the other end of the section; a time element relay having an initial position and an operated position and characterized by a slow movement from its initial position to its operated position only when effectively energized for a predetermined interval, is held at said operated position when subsequently energized eiectively and is reset to its initial position When such energization is momentarily interrupted; decoding circuit means connected with said time element relay and controlled by said track relay and effective to cause such eiective energization of said time element relay only when said track relay is operated by each successive track circuit current impulse, and a signal circuit including a contact of said time element relay closed only at said operated position.

HAROLD G. WI'IMIER. 

